Book/Report

FZJ-2018-03924

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Wachstum versagensrelevanter Oberflächenrisse in oxidischen Keramiken mit und ohne Umwandlungsverstärkung

Dransmann, G. W. (Corresponding author)FZJ* ; Steinbrech, R. W.FZJ* ; Nickel, H.FZJ*

1992
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich

Please use a persistent id in citations: http://hdl.handle.net/2128/19225

Report No.: Juel-2668

Abstract: In recent years active débats are on progress to select the right cracks for determination of the toughness behavior of modern structural ceramics, especially of those exhibiting R-curve behavior. Mostly toughness is measured in notched specimens where cracks grow several millimeters while strength is usually measured with unnotched bend bars where small surface flaws cause brittle fracture. As in the majority of cases the latter cracks are responsible for failure of ceramic components a piezo-mechanic testing machine was designed to observe the growth of "natural" surface cracks in situ and therefrom the mechanical behavior of structural ceramics was studied. The extension behavior of surface cracks ("natural" and indentation cracks) in transformation-toughened ZrO$_{2}$-containing ceramics (stabilized with either MgO or Y$_{2}$O$_{3}$) and non-transforming Al$_{2}$O$_{3}$ was studied. A novel evaluation method was developed to determine the indentation-induced residual stress intensity from experimental data (crack extension curves). In all the cases it was found that failure occurres at toughness levels significantly below the plateau toughness revealed from long crack experiments and this indicates that the use of plateau toughness values overestimates the toughnesspotential of ceramics. For additional information about the microstructure-mechanical properties co-relationship in the ZrO$_{2}$-ceramics Raman-spectroscopy was used. By this means the farfieldtransformation of MgO-partially stabilized ZrO$_{2}$ in bending and the influence of transformation on the indentation crack profile in Yttria-stabilized zirconia was examined.

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Contributing Institute(s):

1. Publikationen vor 2000 (PRE-2000)

Research Program(s):

1. 899 - ohne Topic (POF3-899) (POF3-899)

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Database coverage:

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